(1) Field of the Invention
The invention relates to a method of fabricating a photoresist mask, and more particularly, to a method of fabricating a bi-layer photoresist mask that will improve critical dimension control in the manufacture of integrated circuits.
(2) Description of the Prior Art
Device sizes continue to shrink as semiconductor manufacturing processes are improved. Continuing advancement in the production of ever smaller devices is limited by photolithography techniques. Dry development processes can increase the overall process window for micro-patterning techniques. Dry development processes can improve resolution and depth of focus and result in more vertical resist profiles. However, the critical dimension bias between isolated and dense lines is too large. That is, because of microloading, isolated lines etch faster than dense lines resulting in an unacceptable difference in critical dimension. Also, after dry development in the bi-layer resist process, the resist line edge is very rough. This will cause imprecision in etching.
U.S. Pat. No. 5,545,512 to Nakato and U.S. Pat. No. 5,286,607 to Brown teach a bi-layer resist process in which a silylated layer is formed between the bi-layers. O.sub.2 dry development is used. U.S. Pat. No. 4,882,008 to Garza et al disclose a silylation process and O.sub.2 dry development of the resist using NO as the oxygen source.